Starting from Release 5 (R5), the 3rd Generation Partnership Project (3GPP) provides a High Speed Downlink Packet Access (HSDPA) mechanism to enable high-speed transmission of downlink packets in the air interface. This mechanism adds processing of a MAC-hs layer in addition to the Media Access Control (MAC) layer and the physical layer. The MAC-hs layer comes out of a base station, Node B, and is implemented through interaction between the High Speed Downlink Shared CHannel (HS-DSCH), High Speed Physical Downlink Shared CHannel (HS-PDSCH), High Speed downlink Shared Control CHannel (HS-SCCH), and HS-DSCH Dedicated uplink Physical Control CHannel (HS-DPCCH). The channel features of HS-SCCH, HS-DPCCH and HS-DSCH are configured by the Radio Network Controller (RNC) for a User Equipment (UE) at the time of setting up a radio bearer.
The current protocol stipulates that only the UE in the Cell_Dedicated CHannel (Cell_DCH) state can receive data on the HSDPA related channels. The UE in the Cell_Forward Access Channel (Cell_FACH) state lacks the dedicated control channel and the uplink auxiliary control channel applicable to the HSDPA, and therefore, cannot receive data on the HSDPA related channels. Moreover, the information on the UE in the Cell_FACH state is stored only on the RNC, and the Node B stores no UE information.
In the conventional art, the data communication process of the UE in the Cell_FACH state comes in two modes:
The RNC schedules a resource for the UE, sends the data directed to the UE to the Node B, and specifies the time of sending the data to each UE. The Node B does not schedule the resource, but sends the data to the corresponding UE directly at the time specified by the RNC.
The RNC sends the data directed to the UE to the Node B first. After receiving the data directed to the UE, the Node B schedules the resource and selects a proper time for sending the data to the corresponding UE according to the resource utilization state.
However, in the conventional art, when the UE undergoes certain events, such as cell handover, disconnection, and state transition, the UE notifies the event information to the RNC. However, the Node B is not aware of it and continues to send the buffered UE data from the source cell, which leads to waste of radio channel resources.